Turbine blading



June'9, 1925. 4 1,541,657

0. A. PARSONS. ET AL TURBINE BLADING Filed May 24, 1924 3 Sheets-Sheet le Fmmms W. GAZQN Q C. A. PARSQNS ET AL TURBINE BLADING Filed May 24,1924 3 Sheets-Sheet 2 1 M 22 W W2 June 9, 1925. 1,541,657

' c. A. PARSONS ET AL TURBINE BLADING I Filed May 24, 1924 :5Sheets-Sheet. s

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9 I f I 9 I Nv Y T0125.- QnARLEs A .PAzsMs Patented June 9, 1925.

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CHARLE$ ALGERNON PARSONS ANDFEANCIS VIII-LIAM. GARDNER, 0F NEWCASTLE;Old-TYNE, ENGLAND; SAID Gl-LRDllEl-lt. .EISSIGNO1ti'lOv SAID PARSONS.

TURBINE Application filed May 24,

T0 aZZ whom it may concern.

Be it known that we, CHARLES A'Lonnnou PARSONS and FRANCIS lVILLIAMGARDNER, both subjects of the King of Great Britain and Ireland, andboth residing at Heaton llorlzs, lIewcastle-on-Tyne, in the county offlorthumberland, England, have invented certain new and usefulImprovements in and Relating to Turbine Blading, of which the "followingis a specification.

This invention relates to the blading of turbines.

it is customary in turbines of the reaction type for the blades in thefixed and moving rows to be of the same dimensions and to be spaced.apart by means of suitable distance pieces so that the fluid passagethrough the rotor blades corresponds at all radial distances with thefluid passage througlrthe stator blades.

Further, the fixed and moving blades are somtimes twisted about theirlongitudinal axes so that cross-sections of the blade taken at di'iieront radial distances make ditterent angles with the longitudinal axisof the rotor for the purpose of obtaininga more uni-form. opening alongthe blade or tor the purpose of varying the angle of the fluid dischargealong the lengtl'i of the blade to suit the varying circumferentialspeed. In such cases also the steam pa, sage can be made to correspondin adjacent fixed and moving rows at all corresponding radial positions.

In some cases, however, it is found expedient to make the rotor bladestaper in thickness from the root to the tip in order to l ease thestress at the root caused by centrifugal force. In such a case thecorideuce between the adjacent fixed and moving blades no longer exists,so that in nontwistral blades the fluid passage through the tired bladescannot be made the same as that through the moving blades at allcan-responding radial distances, the result being a diflerence in thevelocity of the steam relatively to the blades in the case of the bladesof the rotor and stator respectively. and also a lateral displacement ofthe fluid in passing between the adjacent fixed and moving rows with aconsequent loss of e'flicien'cy.

In the case of the twisted blades, tapering of the rotor blades causes asimilar READING.

1924. SeriaL No. 715,838.

lack of correspondence in the fluid passages. iii in such a case theamountof twist of either st'ator or rotor blades is increased ordecreased so as to make the discharge opening of the fluidpassages-equal at corresponding points, a further ditiiculty" isencountered, namely, the angle of discharge of the fluid no longercorresponds at all radial points to the circumferential velocity of theblades.

The object of the present invention is to overcome these diiiicultics.

lVil'h such an object the invention consists in the improvementsinturbine blading hereinafter described and particularlypointed out in theclaims.

deter"ring to. the accompanying drawings which are to a certain extentof a diagramn'iatic nature Figure 1 shows a sectional elevation throughpart of an. axial-flow reaction turbine;

Figures 2, 3 and 4*" being cross-sections through adjacent blades takenrespectively on the lines 22, and, 4 l of Figure 1 to show the taper ofthe blades, and

Figure 5 a corresponding sectional perspective view of one of the statorblades;

ligures 2P, 3" and 4" are cross-sections also taken respectively on thelines 2+2, 3+3 and of Figure 1 of i1,.1110dlfi02'.' tion in which thetapered blades are also twisted;

Figure 6' being a corresponding sectional perspective view of one of thestator blades, finally v Figure 7 shows a sectional elevation through.part of an axial-flow. reaction. turbine, in which the stator and rotorblades are of diilerentwidths', while Figures 8, 9 and 10 arecross-sections respectively on the lines 8S, 9'-9'and 10- 10 of Figure7.

In each of the Figures 2 3? and t, 2*, 3 and t" and 8, 9 and 10, thestator blades are shown above and the rotor blades below, while the samereference letters are used throughout to denote corresponding parts inthe diii'erentv figures;

In carrying theinventio'n into effect according to one form as shown inFigures 1, 2, 3,- 1 ando applied to an axial-flow reaction turbinm thespaced rotor blades, a, are secured in any suitable manner tothe rotor,b, and as shown by the cross-section in Figures 2, 8 and l decrease inthickness from root, a, to tip, (0 in order to lessen the stress due tocentrifugal force. Similarly, the stator blades, 0, spaced to correspondare suitably secured to the stator body, d, but as shown in Figures 2 3and at, decrease in thickness from tip 0, to root, 0, their thicknessbeing equal to that of the rotor blades at equal radial distances. InFigure 5, a perspective view of such a stator blade is shown decreasingin thickness from the tip, 0 to the root end, 0, where it joins theroot, (2, itself. By so proportioning and arranging the stator and rotorblades, it will be seen that the thick tips, 0 of the stator bladescoact with the thick roots, a, of the rotor blades and the thin roots,0, of the stator blades with the thin tips, a", of the rotor blades, sothat the fluid passage through the stator blades corresponds at allradial distances with the tluid passage through the rotor-blades.

According to a modified form of the invention, the stator and rotorblades as re gards thickness and relative arrangement are as abovedescribed but in addition, as

shown in Fi ures 2? 3 and d are twisted about their longitudinal axes soas to make the angle of discharge of the fluid correspond at all radialdistances to the circumferential velocity of the blades. As the sectionof the stator blades at any radial distance is the same as the sectionof the rotor blades at the same distance, the twisting of the bladeswill not alter the corre sponding steam passages between the rotor andthe stator blades, and thus no loss in efiiciency will be incurred.

In Figure 6, a perspective view of such a twisted stator blade is shown,the thick tip being indicated at 0 and the thin root end at 0.

Further, in some cases, either to meet special stress conditions or forsome other reason, it is convenient to adopt a stator blade of differentwidth from the rotor blade. Thus, as shown in Figures 7 to 10, thestator blade, f, is of less width than the rotor blade, a, but decreasesas before from the maximum thickness at the tip, F, to a minimumthickness at the root, 7'. The rotor blades, as before, decrease inthickness from the root, a, to the tip, (L2. In this case, as seen inFigures 8 to 10, the stator blades, 7', are more closely spaced than therotor blades, a, so that the passages, it, for steam flow between thestator blades may be geometrically similar, or approximatelygeometrically similar, to the passages, 2", between the rotor blades.

The rotor and stator blades may be provided in the first place with therequired taper or they may be tapered by any suitable means from bladesof parallel section produced by any known method.

Having now described our invention, what we claim as new and desire tosecure by Letters Patent is 1. In combination in a turbine, relativelyrotatable co-axial blade-carrying elements, outwardly-projecting bladesdecreasing in thickness from root to tip carried by one of saidelements, and co-acting therewith inwardly-projecting blades decreasingin thickness from tip to root carried by the other of said elements, asset forth.

2. In combination in a turbine, co-axial stator and rotor elements andco-acting blades carried by said elements, said blades carried by saidrotor element decreasing in thickness from root to tip and said bladescarried by said stator element decreasing in thickness from tip to root,as set forth.

In combination in a turbine, relatively rotatable co-axialblade-carrying elements; o1itwardly-projecting blades twisted abouttheir longitudinal axes carried by one of said elements, and co-actingtherewith inwardly-projecting blades twisted about their longitudinalaxes carried by the other of said elements, said outwardly-projectingblades decreasing in thickness from root to tip and saidinwardly-projecting blades decreasing in thickness from tip to root, asset forth.

4. In combination in a turbine, relatively rotatable co-axialblade-carrying elements; outwardly-projecting blades decreasing inthickness from root to tip carried by one of said. elements, andco-acting therewith in wardly-projeeting blades decreasing in thicknessfrom tip to root carried by the other of said elements, saidoutwardly-projecting and said inwardly-projecting blades having the samethickness at equal distances from the axis, as set forth.

5. In combination in a turbine, relatively rotatable (Jo-axialblade-carrying elements; outwardly-projecting blades decreasing inthickness from root to tip carried by one of said elements, andco-acting therewith in wardly projecting blades decreasing in thicknessfrom tip to root carried by the other of said elements, saidoutwardly-projecting and said inwardly-projecting blades decreasing inthickness at the same 'rate, as set forth.

(5. A turbine stator blade thicker at the tip than at the root, as setforth.

7. A turbine stator blade thicker at the tip than at the root andtwisted about its longiudinal axis, as set forth.

In testimony whereof we have signed our names to this specification. 7

CHARLES ALGERNON PARSONS.

FKANCIS XVILLIAM GARDNER.

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